1 Center for Molecular Biology, University of Vienna, Max F. Perutz Laboratories, Doktor-Bohr-Gasse 9/4, A-1030 Vienna, Austria. Electronic address: manuela.baccarini@univie.ac.at.
2 Institute of Biochemistry II, Goethe University School of Medicine, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Riedberg Campus, Max-von-Laue-Straße 15, 60438 Frankfurt am Main, Germany; Institute of Immunology, School of Medicine, University of Split, Mestrovicevo setaliste bb, 21 000 Split, Croatia.